Low water detector for boilers



Aug. 8, 1933. w. o. LUM 1,921,684

4 LOW WATER DETECTOR FOR BOILERS Filed July 1, 1951 Fi p l.

Inventor: \A cllce'r- O. Lum,

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Patented Aug. 8, 1933 1,921,684 r LOW WATER DETECTOR FOR BOILERS Walter O. Lum, Schenectady, N. Y., assignor to General Electric Company, a Corporation of New York Application July 1, 1931. Serial No. 548,205

9 Claims. (01. 122504.3)

My invention relates to heating apparatus, more particularly a safety device therefor for detecting low water conditions in a boiler.

Heretofore it has been the usual method to employ floats for detecting dangerously low water conditions within the boiler. It has been necessary to provide a separate float chamber on the outside of the boiler due to the culty of providing a proper locationwithin the 10 boiler for the float. Temperature .responsive devices have also been used for the purpose of detecting low water conditions. It has been difficult in this case also to provide a suitable location for this sort of detector. The sole purpose of such low water detecting devices is to protect the crown sheet. 7 of the boiler. Hence, it is desirable to provide a detecting means which will notify the attendant or automatically shut off the heating supply just before such low water conditions are reached as-will prove destructive to the crown sheet.

Briefly, my improved form of low waterdetecting device consists of a well within the boiler and extending through the crown sheet. Communicating passages between the interior of the well and the boiler are provided so that the level of the water within the well will follow the level of the water within the boiler until a predetermined low level is reached. Due to the fact that no more water can enter .thewell from the boiler after this low level is reached, the heat within the combustion chamber rapidly converts the water in the well to steam. A temperature re? sponsive bulb placed in the well responds to the rapid increase in temperature due to this rapid vaporization of the water within the well to operate-a metallic bellows member which in turn operates 'a switch to break the circuit to a heat supply means such, for example, as a gas burner or an oil burner. In the bottom of the well is provided a fusible plug. The purpose of this plug is to open the end of the well into the V combustion chamber of the boiler should 'the safety switch fail to function to cutout the fuel I thus cutting off the supply of heat.

In the drawing,rFig. 1' shows the application of my invention to a boiler. Fig. 2' shows the with the combustion chamber.

thus permitted to enter the combustion chamber which will under ordinary circumstances either details thereof. Referring specifically to the drawing, the boiler 10 is provided with a combustion chamber 11 and a flue 12. Heat is furnished to the combustion chamber by means I of the oil burner 13 which is energized from the supply lines 1; and 15. A safety switch 16 controls the circuit to .the supply line 14. This safety switch is controlled by means of the safetydevice designated generally at 17, which consists of the well casing 18 mounted in'the 5 crown sheet 19 of the boiler and etxending into the combustion chamber-11. A thermostatic bulb 20 is filled with a liquid which expands and contracts in response to temperature changes within the well 18. This bulb 20 is connected to a metallic bellows member 21 by means of the tube 21". A fusible plug 23 i mounted in the bottom of the well.

mThe detailsof the well and temperature responsivedevice are shown in Fig. 2. The well 18 is provided with the fusible plug 23, as shown, in the bottomthereof. Two series of holes 24 and 25 are provided in the sides of the well for communication between the interior ofthe well and the boiler. This permits water in the well and in the boiler to follow each other until the water in the boiler falls below the lower holes 24. The communicating tube 21' extends through the top of the well which is provided with the cap member 26. A washer member 27 ofproper material is held in place against the cap member 26 by the plug member 28 to form a steam seal between the well andthe exterior of the boiler. r C

In operation, when the water level within the boiler falls belowthe holes 24 due to the inability of the supply within the well to be replenished from the boiler proper and due to the heat absorbed by the bottom of the well and plug which extend into the combustion chamber, .the water is quickly transformed to steam. The bulb 20 being no longer surrounded by water, quickly responds to the change in temperature" within ie well to operate the switch lfi'against spring 22 which normally biases switch 16 to closedposition. This opens the circuit through the oil U burner motor and, cuts 01f the fuel supply. If for any reason the safety switch 16 fails to open, the intense heat from the combustion chamber will soon rais'ethe temperature of the fusible I plug 23 to its melting temperature.

This opens the bottom of the well and connects the boiler The steam is put out the flame or prevent the temperature of the crown sheet from being raised to excensive temperatures. The steam escaping from the combustion chamber will soon draw attention to the fact that dangerously low water conditions have been reached. It will thus be seen that I have provided a simple and effective low water detector of improved design.

- The embodiment of the invention illustrated and described herein has been selected for the purpose of clearly setting forth the process involved. It will be apparent, however, thatthe invention is susceptible of being modified to meet the different conditions encountered in its use and I therefore intend to cover by the appended claims all modifications within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:-

1. A safety device for detecting low water conditions in a boiler having a water well in said boiler extending through the upper wall of said boilerinto'the combustion space and in which the water level follows the level within said boiler until the water falls below a predetermined level, the level of the Water in said well thereafter falling more rapidly than the level in said boiler, means containing a thermal responsive fluid located in spaced relation with the walls of said well to be responsive to the rapid increase in temperature thereof when the water well boils dry, a tube connected with said means and extending out of the top of the well through an exterior wall of the boiler and sealed therein, and automatic safety means connected with said tube to be operated by fluid. I

2. A safety device for detecting low water con ditions in a boiler having a well within the boiler extending through the crown sheet thereof, said well having communicating passages to the boiler arranged whereby the level of the water in said well and said boiler remains the same until the water falls below a predetermined level, the water in said well thereafter being quickly evaporated therefrom and a heat responsive element for shutting off the heat supply when said water is quickly evaporated from said well, and a fusible plug in the bottom of said well, said plug operating to open the well in case of failure of said heat responsive means whereby the steam from said boiler is discharged into the combustion chamber of said boiler to prevent heat being supplied thereto.

3. A safety device for detecting low water conditions in a boiler, having a tubular sealed casing extending from the exterior of the boiler through the steam space of the boiler and the crown sheet and providing a well in said boiler extending into the combustion chamber thereof, said casing having means for maintainingthe water the casing level with the water in the boiler until the water falls below a predetermined level, the level of the water in the well portion of said casing thereafter falling more rapidly than the level in said boiler, a bulb containing a thermal responsive fluid located adjacent the walls of the well portion of said casing extending into the combustion chamber to be responsive to the rapid increase in temperature thereof when the level of the water in the well falls more rapidly, than the said thermal responsive and automatic safety means having an expansible bellows connected to the otherend'of said tube to be operated by said thermal responsive fluid.

4. A safety device for detecting low water conditions in a boiler having a tubular sealed casing extending from the exterior of the boiler through the steam space of the boiler and'the crown sheet and providing a well in said boiler extending into the combustion chamber thereof, a series of communicating passages in said casing for connecting the interior of the well and the boiler whereby the level of the water in said well and the boiler fall together until a predetermined level is reached, the water in said well thereafter falling more rapidly than the water in said boiler due to increased vaporization of the water in said well, a bulb containing a thermal responsive fiuid located in spaced relation with the walls of said well to be responsive to the rapid increase in temperature thereof when the level of the water in the well falls more rapidly than the level of the water in the boiler, a tube having one end connected with said bulb and extending through an exterior wall of the boiler and sealed therein, and automatic safety means connected with the other end of said tube to be operated by said thermal responsive fluid.

5. A safety device for detecting low water conditions in a boiler having a well in said boiler extending into the combustion chamber thereof, a series of communicating passages for connecting the interior of the well and the boiler arranged whereby the level of the water in said well and the boiler fall together until a predetermined level is reached, the water in said well thereafter falling more rapidly than the water'in said boiler due to increased vaporization of the water in said well, and a thermostatic device in said well responsive to the rapid'fall in the level of the water in said well for shutting off the heat supply, and a fusible plug in the bottom of said well for opening the well into the combustion chamber upon failure of said thermostatic device to function, whereby the steam from said boiler is discharged into the combustion chamber to prevent heat being supplied thereto.

6. A low water safety device for combustion boilers comprising a water well mounted in the upper wall of the boiler and extending into the water space above said upper wall andbelow' said upper wall into the-combustion space, a bulb containing a thermal responsive fluid located in spaced relation with the walls of said well to be responsive to the rapid increase in temperature thereof when the water well boils dry, a tube connected with said bulb and extending out of'the top of the well through an exterior wall of the boiler and sealed'therein,

, and automatic safety means connected with said tube to be operated by said thermal responsive fluid. v

7. A low water safety device for combustion boilers comprising a tubular sealed well casing extending from the exterior of the boiler through the steam space and the crown sheet into the combustion space of the boiler and hav ing openings therein' communicating with the water in the boiler when the water is above a predetermined level, a bulb containinga thermal responsive fluid located adjacent the walls of I the portion of said well casing extending into the combustion space to be responsive to the rapid increase in temperature thereof when the water level of the boiler falls below said predetermined level, a tube communicating with said bulb and extending through a seal at the top of said well casing and automatic safety means having an expansible bellows connected to the exterior end of said tube to be operated by said thermal responsive fluid.

8. In combination, a boiler having a combustion chamber, a burner for supplying heat to said combustion chamber, a water well mounted in the crown sheet of said boiler and extending into the water space above said crown sheet and into the combustion chamber below said crown sheet, a bulb containing a thermalresponsive fluid located in spaced relation with the walls of said well to be responsive to the rapid increase in temperature thereof when the water well boils dry, a tube connected with said well and extending out of the top of the well and through an exterior wall of the boiler and sealed therein, and automatic safety means connected with said tube to be operated by said for supplying heat to said combustion chamber,

a water well mounted in the, crown sheet of said boiler and extending into the water space above said crown sheet and intothe combustion chamber below said crown sheet, a bulb containing a thermal responsive fluid located in spaced relation with the .walls of said well to be responsive to the rapid increase in temperature thereof when the water well boils dry, 8. tube connected with said bulb and extending out of the,

top of the well and through an external wall of the boiler and sealed therein, and automatic safety means including a switch connected with said tube to be operated by said thermal responsive fluid for controlling energization of,

said burner.

- WALTER O. LUM. 

